1. Field of the Invention
The present invention relates to a disk driving apparatus and a method for operating a disk driving apparatus for recording or regenerating data with respect to a disk media which is served for recording data handled in a computer or the like.
2. Description of the Related Art
On a disk media such as an optical magnetic disk or the like, reference clock patterns are formed preliminarily in manufacturing process. The reference clock patterns are formed in the circumferential direction of respective tracks at a given interval. A disk recording/regenerating apparatus which records/regenerates data with respect to a disk media sequentially reads the reference clock patterns on the disk media which is rotated at a given speed and obtains reference clocks which are synchronized with the appearance of the patterns. The disk recording/regenerating apparatus generates sampling clocks by multiplying frequency of the reference clocks and records or regenerates data with respect to the disk media in synchronization with the sampling clocks. This type of method is referred to as an external clock system.
In the external clock system, processing for generating the sampling clocks and the processing for recording data and regenerated data are made independent from each other. Accordingly, in the disk recording/regenerating apparatus adopting the external clock system, it is necessary to correct the displacement of phase between the sampling clock and the data and hence, the disk recording/regenerating apparatus includes a variable delay circuit which performs the fine adjustment of the phases of the sampling clocks (for example, patent documents such as Japanese Unexamined Patent Application Publication No. 2004-87026).
The reference clock patterns are formed radially on the disk media. Accordingly, the interval of the reference clock patterns is shorter at the inside of the disk media. A rotational speed of the disk media, for recording/regenerating data in a stable manner without depending on the access position, is set to a low value when the apparatus gets access to the tracks on an inner peripheral side and is set to a high value when the apparatus gets access to the tracks on an outer peripheral side. Further, the recording frequency (frequency of sampling clocks) of data is set to a lower value as the access point approaches the inside of the disk media. Accordingly, the number of delay stages of the valuable delay circuit is set corresponding to the recording frequency of the data on the inner side of the disk media which has the longest cycle.